[RFC] entry: Untangle the return value of syscall_enter_from_user_mode from syscall NR

[Thomas Gleixner]

On Wed, Jul 01 2026 at 19:42, Michal Suchánek wrote:
>  
>  	if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT))
> -		syscall = trace_syscall_enter(regs, syscall);
> +		*syscall = trace_syscall_enter(regs, *syscall);
>  
> -	syscall_enter_audit(regs, syscall);
> +	syscall_enter_audit(regs, *syscall);
>  
> -	return ret ? : syscall;
> +	return 0;

That breaks trace_syscall_enter() because the probes/BPF muck attached
ot that can:

     1) set the return code
     2) set syscall to -1L

That works correctly today, but with your sloppy hackery the low level
x86 code falls into sys_ni_syscall() which sets the return code to
-ENOSYS.